The present invention is directed to an electrically programmable fuse (“e-fuse”) module in a semiconductor device.
An integrated circuit semiconductor device (“IC”) may include one or more e-fuse modules, which can provide non-volatile memory (NVM) for data. E-fuse modules include arrays of fuse elements that can be individually programmed electrically (i.e., blown) after manufacture of the IC, and even after delivery of the manufactured IC, to define corresponding bits of the stored data as asserted or de-asserted. E-fuse modules may be used to store lot number and security data on the IC or to configure interconnections of elements of a field-programmable gate array (FPGA) by the customer or designer after manufacturing.
An e-fuse module may be programmed by applying a relatively high current briefly to change the original resistance of selected e-fuse elements, defined by design and manufacturing parameters, to a programmed resistance that is a function of the programming current. The programming current typically produces a substantial increase in the resistance of the e-fuse element, although the programming current reduces the resistance of the fuse elements in the case of anti-fuses, for example. The difference of resistance between the two states of an e-fuse element is typically at least an order of magnitude, and may for example be 200 Ohms in the low resistance state and 100,000 Ohms in the high resistance state.
An e-fuse module includes a programming current generator that provides an adjustable current for programming the elements of the e-fuse array. Control of the programming current controls the resistance of the programmed e-fuse elements. An e-fuse module also includes a sensing system that can be used to sense the resistance state of the individual elements of the e-fuse array to output stored data and/or for testing whether the asserted and de-asserted resistance states of the e-fuse elements are within specification.
It is known to use an array of reference resistors in generating an adjustable reference current or voltage for the programming current generator. However, such an array of reference resistors occupies an undesirably large area of the IC. Accordingly, it would be advantageous to have a more compact e-fuse module.